LEDs and Voltages
LEDs and resistors in series are common in our daily life, but how does it work? Here we explain a problem you may face.
Suppose you have stumbled upon this confusion about series circuit. That you have two 3V LEDs connected in series to a 12V battery. What will happen then? Because the first LED would have 9V across it and the second one 6V, so you may wonder is it possible to burn them? If you use a resistor, it will lower the available volt for the second LED, but how will you make it work?
Actually, an LED will always try to get its specified voltage across itself. Two 3V LEDs in series, connected to a 12V battery will force a lot of current through the LEDs and they will burn out. When you put a resistor into the circuit, the two LEDs will have 3V across each, and the remaining voltage will be across the resistor. Then you can use Ohm’s law to find the proper resistor for the current you want. For the most common LEDs, you can usually aim for 15-20 mA.